Looking Up: Seeing a fireball: A really bright meteor

You never know when you might catch a really big one! I could be talking about fishing, but in this instance it is a whopper of a meteor.

A fireball is a rare, extremely bright meteor. Of varying magnitude, they are not stars at all. They are larger rocks that are caught up by Earth’s gravity, and make it through a much larger portion of the Earth’s atmosphere. Those that don’t completely vaporize, as this one apparently did, strike the Earth. The remainder that reaches the ground is what is called a meteorite.

Anyone else who may have witnessed a fireball is welcome to contact me with a report. Very large fireballs will briefly lighten the night sky and can even be seen in broad daylight.

Much more common, of course, are the dimmer variety, the meteors we might see on any clear night streaking across the sky. They never fail to startle and amaze. There are many meteor swarms that collide with the Earth’s atmosphere on expected times of the year. Referred to as meteor showers, most are sparse but a few typically put on impressive shows. Other meteors arrive at random, not necessarily connected with a known shower.

They may vary in speed, brightness and hue. Brighter ones typically have a trail behind them which usually vanishes as quickly as the bright “head.”

These “space rocks” range in size from small grains of sand to around three feet wide. Most of them are pieces from a comet or an asteroid. They strike the Earth’s atmosphere at speeds of greater than 45,000 mph. Most meteors become visible around 47 to 75 miles above Earth and fully disintegrate around 31 to 59 miles up. The air in front of the meteor becomes compressed, and its temperature rises. The meteor heats up so much that it glows, and quickly consumes the rock.

The International Meteor Organization classifies a fireball as a meteor as bright as -3 magnitude or greater, when seen straight up (at the zenith). The bright star Vega, seen high in the west on November evenings, is magnitude 0. The brightest the planet Venus reach is -4. The full Moon is -12. Fireballs reaching magnitude -14 or greater are called bolides.

One of the strongest meteor showers of the year is the Geminids, which peaks Dec. 13-14. Seemingly radiating from the constellation Gemini, about 75 an hour may be seen under a moonless, rural sky, after midnight. Meteor showers tend to be at their best after midnight because the morning side of the Earth is hitting the meteor swam head-on as the Earth moves in its orbit.

For more information visit the American Meteor Society at www.amsmeteors.org.

New Moon is on Nov. 18.

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Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.